What Test equipment should I have and what tools should I have on my workbench?

If you’re starting from scratch, there are a number of things you’ll need to have.

Multi Meter

As far as test equipment, you need to have a good Voltmeter. Notice I didn’t say digital, I said “good”. So how do I define good? Well it needs to have a high input impedance. A bare minimum sensitivity of 20kΩ/volt, the higher the better.  Most digital multimeters and VTVM (Vacuum tube volt meters) have an input impedance of 10MΩ.  Note that since the input impedance is constant, the sensitivity will change depending on the voltage range chosen.

It would be nice to have two multi-meters when you’re working on power supplies and doing initial check on equipment.  Seeing the current and voltage change can be very helpful. This is not essential to start and I would wait if you’re building up from scratch.

Oscilloscope

This is not essential to start with, but rather something you should keep your eye on. I have one that is almost 30yrs old now, which I’ve owned since it was new. Probably a basic thing to look for is 20MHz bandwidth and dual trace capability. Beyond that there are tons of features to look for and I could devote a whole set of articles t choosing a scope.

Soldering Iron

There are tons of options to choose from. Here is a good resource that you can use. I started with a 25Watt pencil iron and used that for many years. I even build a computer that involved soldering literally thousands of pads without a problem. This resource has several DIY options if you don’t want to spend the “big bucks.”

If you’re doing lots of troubleshooting, a de-soldering iron or at least an anti-static de-soldering pump are going to be key.

dummy load

For testing power supplies, especially SMPS you will need a dummy load to properly test it. See this article on building your own.

ESR tester

As you do more and more testing, the ESR meter will become an essential tool in evaluating capacitors. It can quickly tell you whether a cap is good or bad. Additionally, since they do such a good job of measuring low resistances, they can help you find and identify cracks or breaks in PCB traces.

Variable DC power supply.

I suggest something that can provide 30 to 50 volts DC and somewhere between 3 to 10 Amps of current. A very useful and I would almost insist as essential is a current limiting capability. The reason is if you’re testing a suspect circuit, it is nice to prevent it from burning to a crisp by virtue of over current. Similarly, a high output current capability is key in some testing circumstances. (You may want to intentionally stress a circuit)

Frequency Counter

Another useful though certainly not essential for a beginning test bench is a frequency counter. I have a 500MHz capable unit with a high stability crystal reference oscillator. Some multi-meters have a frequency counting capability up to 10 or 20MHz. This will likely suffice for most requirements. I do a lot of work with radio transmitters and receivers so find the counter very helpful.

To summarize, the “good” multimeter is the first piece of test equipment you should focus on acquiring.
Good luck, let me know how it goes.

Way back when, before wife and kids, after college, 1985 to be exact I bought a microwave oven. It was a Sharp model with a rotating carousel. The carousel was rather unique, and most ovens didn’t have one. You were required to stop cooking and rotate the food periodically to ensure even heating. The carousels rotation helped to minimize that. It was a 600 watt model and it served me well for several years and then my family for many years. We got rid of it after twelve years because of low or changing power. Some times it seemed to cook with it’s usual gusto other times it was downright anemic.

It was Replaced by a Panasonic Turbo Inverter.
An unusual thing was that it would sometimes change rotation directions. Not always and not consistently. Believe it must had a “synchronous” motor I’ve seen that before, but doubt they would put such a motor in a microwave. I mean, why??

Just after two years, a switch went bad and it would no longer turn on. I opened it up to find not 1, not 2, but 3?! switches wired in series with the door. It wasn’t like there was one switch for the top of the door and one for the bottom or different physical locations. They were all fairly close to each other and in the same relative area. After figuring out which swtich was bad, I found out that the one I needed to replace was the $28 one. The other two were more reasonably priced at $5. I decided two was more than enough and jumpered around the broken one rather than paying $28 for a replacement switch. Everyone in the household was instructed to not use the door switch to turn off the microwave. Stop it from the control panel then open the door. That lasted about another year.

Died on 3/23/2011. arcing sounds heard and the burning phenolic odor was prolific. Came home and tested it ran about 12 seconds and then made a couple of snap crackles and then shut off. Disassembly revealed plenty of burned up stench though I couldn’t see anything obvious other than several connections that had been severely overheated. (blackened plastic and oozing pools of goo)

Wife went out and bought a new one, a Sharp carousel. This one is rated at 1100Watts (IEC) and the first check by me was 952 watts. (12oz water from 59F to boiling in 2 min 10 seconds)
I’ll try that again with a styrofoam cup as it is lower mass.

Disassembly was sad as the “inverter” meant there was no big transformer for all my “someday” High voltage experiments.

Most people believe that troubleshooting an electronic circuit is a simple matter of connecting an oscilloscope or multimeter to a circuit and then fixing something. Let me tell you it’s not quite that easy. I think circuit design and troubleshooting are very similar in a lot of respects. In troubleshooting a circuit, you have to discern what a circuit is supposed to do. Once you know that you may or may not be able to tell if it’s broken. You try to change a parameter on the input side of the circuit and see if the output changes correspondingly.

When I do a design, if I’m starting in the middle because of a performance issue or other constraint, I work towards the side of the circuit I feel is going to be more difficult. The reason I do that is I want to do the hard part first.

Troubleshooting	Design

I have both of the books above and can highly recommend them both. The troubleshooting book is by Robert Pease. He has a plethora of analog knowledge and has been a senior staff engineer at National Semiconductor for a long time. His experience is not only in design but application. If a customer had an issue with a circuit design and called NS it would not be uncommon for them to get to speak with Bob. But don’t just take my word for it. Currently over 75% of the reviews on Amazon are 5 star. Over 90% of the reviews are 4 star or better.
There are NO bad reviews.

The design book, Art of Electronics, is also a great book. I wish I had the book when I was taking my EE coursework back in college. It is in an excellent reference from the standpoint that just about any information you would ever want about electronic design is in the book. However, the index in the book is not very well done. So if you ask where is “X” or “Y” you probably won’t be able to find it. Even so this is an outstanding book. While reading it, I recommend that you have a tablet or notepad that you can note the topic and page number.

Just yesterday, one of the computers in the house wouldn’t turn on… All the computers are set to run diagnostics at night and then turn off. If I’m the last one up at night, I’ll turn off the UPS for the associated computer. Since I’m not usually the last one up it doesn’t happen that often. My wife figured that out, turned on the UPS and the computer still wouldn’t turn on… So it became a project.

Step one for me is

Simple Tester	GFCI Tester

The first thing I did was to verify that I had power at the wall, then all of the sockets on the UPS. Everything checked out OK, so it’s time to disassemble the computer. Since I’m taking it apart, I got out my vacuum cleaner and the adapter kit. I’ve had the kit for almost as long as the socket tester. I’ve added a stiff craft paint brush to it. The brush is about 5″ long so fits in the bag with the other items. I got mine from my wife after she completed a craft project. You can buy them at any craft store. What you want is soft, yet stiff. If the brush is soft, but not stiff enough and the bristles are long, you can use scissors to cut the bristles to a shorter length. The bristles on my brush are just under 1/2″ long. Small is good because you want it to fit into tight places. If you don’t have a standard vacuum you could buy one of these “electronics” vacuum cleaners. Even if you’re going to have a business doing repairs, I don’t recommend one of these. I would much rather have you get a good canister vacuum and the adapter kit. It is much more useful. It’s presented here as an option/alternative.

Attachment Kit	Brush	Small Vacuum

I also bring in my compressed air cans or my air compressor. Here are a couple of suggestions. If you are going to use the air compressor, you need to make sure that it is only sending out air and not oil too. Set it up and find a clean white cloth/rag. Put the cloth over the end of the air discharge and discharge the compressor through the cloth for about 20 – 30 seconds. When done, look at the cloth if it shows oil or dirt, DON’T use it on your computer. My compressor is similar to the one shown, I bought it at Costco with all the accessories, including a 20ft curly hose for under $100.

If you’re using the cans of compressed air, you’ll notice the pressure drops as you use them and the cans get very cold. This is normal and due to the laws of thermodynamics. What you can do is keep the can in a pan of warm, NOT HOT, water. If you can’t keep your hand in the pan of water with the can, the water is too hot. Warning: using too hot water will cause it to explode. You have been warned!

Canned Air	Air Compressor

As I disconnected each of the cables from the computer I cleaned everything using a regular household cleaner like Formula 409 or Fantastik. I set them aside. Once everything was disconnected I vacuumed the computer using the regular vacuum. Opening the computer I again used the big vacuum. Placing it on one side of the fins of the heatsink, I injected pulses of air in from the other side of the heatsink. Similarly, I put the vacuum on one side of the drives and injected the air from the other side. After doing that, I added the attachment kit to the vacuum and cleaned the circuit board and all the areas of the computer. Be very careful not to break anything.

If you plan on disconnecting anything from inside the computer, you should have an antistatic wristband on and have the computer on an antistatic mat. Similarly, you should have anti-static bags to put the removed components into. I have a bunch of large, resealable bags that I use. If you want you can get an assortment of sizes, but for our purposes big bags are fine because the storage is temporary.

Anti-Static Wrist Strap	Anti-Static Mat	Anti-Static Bags (Resealable)

Now that everything has been cleaned, I tried to power it up. No joy.

I carefully disconnected the power supply from the components and then from the mother board. When disconnecting from the mother board, be careful to depress or open any retaining clamps as appropriate. I’ve seen both styles of connectors one that has to be pinched to open and those that have to be spread apart to “unlock.” Remove any screws that hold the power supply to the chassis. Carefully remove it. I then removed the screws holding the power supply case together. Once open, I used the vacuum and compressed air to clean it out. Once clean, I used a bright light and carefully inspected it for any signs of damage or burned out connectors. Seeing none, I again plugged in the power supply. This time, the green “power available” L.E.D. came on! I unplugged it and then reattached the cover. I again plugged it in and again the green “power available” L.E.D. came on. So I put the power supply back in the chassis and again plugged it in. I still have the green LED lit. Now I re-attached each of the power cables from the harness to the components while observing the LED. No problems as I attached it to each of the drives. I attached the first, smaller, harness to the motherboard no problems. As I attached the larger harness to the board, I noticed that the LED flickered as I inserted the plug into it’s receptacle. Luckily(?) the LED remained on. Now I pressed the power switch and the fans came on and the drives started to spin up. I immediately turned the power off and closed up the case. Re-attaching all the cables I set the computer up and we were off and running again.

Why National Fine (NF) as opposed to National Coarse (NC) when using threaded fasteners?

Strength!

The reason is strength. If you compare the strength of similarly sized fasteners, the one with National Coarse (NC) versus National Fine (NF) threads, you’ll see that the NF threaded fastener is between 10% and 20% stronger than the NC version. As rule of thumb, the NF part is about 15% stronger than the NC part.

Why not just go with a larger fastener?
Your part is likely constrained in size of penetration that it can accept or the size of the fastener would interfere with adjacent parts. In the case of my large screen LCD set, I don’t know why as the piece that they threaded was in no way limited in size. Similarly, the case mold could have been increased in size to take care of the increased fastener size. I think it was likely an oversight on their part and they chose to increase the strength by changing the thread pitch instead of remaking the mold… Just a guess on my part. Thankfully, the legs were made out of aluminum so it was relatively quick to drill and tap the threads in the piece.

I have a 42″ LCD TV made by Olevia. Just after it finished it’s warranty period it died. I didn’t have time to devote to fixing it because of other commitments so I took it to a shop for repair. After looking it over, the owner told me it would cost $300 to fix because it needed a new main board. I agreed and it was fixed.

After having it back for a few months, it started quitting after being on for some period of time. It appeared to be heat related because if I restarted it it would quit again in less time than the first. This would continue until it would shut off within minutes of being re-started.

Taking it apart was fairly straight forward until I got to the four screws that, in addition to attaching the case, attached the chassis to the legs of the stand. I fought with these screws for quite some time and was unable to get one on each of the two legs out. The two that I did get out were bent, one rather dramatically. The other two screws refused to budge, how was I going to get this thing opened up? I resigned myself to the fact that I was going to have to cut the case off near the legs. While I had several options the one I chose was to use a large (85watt) soldering iron to melt the case around the legs.  It seems that the “professional” I used to repair my set was unable to get the screws to go back in properly so he just “persuaded” them.  Two of four holes in the stand were stripped out.  Drat!!

After getting the set open, I took pictures for ease of reassembly. I removed and categorized the screws. See TROUBLESHOOTING TIPS for ideas on storage. Testing quickly proved the power supply was the culprit. I searched high and low and scoured the internet for schematic diagrams. Olevia’s idea of a service manual is a joke. It is what one would expect to give to a consumer. For example:
Problem: Set won’t turn on

Possible solutions:

• Is it plugged in?
• Is the Master power switch turned on?
  • Replace the power supply

It doesn’t even tell you to check the fuse in the power supply! What kind of “service” manual is that? I replaced the fuse and on restoring power was greeted with a BRIGHT flash and a blackened fuse. Something was seriously wrong! I went through the supply looking at the electrolytic capacitors with my BLUE ESR meter and found no bad ones and one that I couldn’t decide if it was good or bad. I ordered a replacement capacitor from Digi-Key, I was able to get an exact replacement. When it arrived, I checked it on the ESR meter and the reading was identical to that of the one in the power supply. No interpretation required. I attempted to overdrive the power supply with my variable DC supply but my variable supply can only deliver 3 Amps which is what the unit was fused at. After loading for several minutes the only part that got warm was a diode rectifier bridge. I’ve never seen one of these go bad before so didn’t have high hopes. Upon removing it, my hunch proved correct the bridge was fine.

I tried tracing the circuit using the Blue ESR meter with no luck. I finally gave up and did a web search for a replacement power supply. I found two merchants that offered them for just under $200 but had none in stock. I went to eBay and found that one had been sold in the last 3 months for $115. I saved a search for it and waited. About 3 weeks later I was alerted to one that was up for auction. I asked the seller how he came about it and his set died just like mine did before I took it to the shop. I bid and won for $59.

I installed the new power supply and did a “smoke” test. The smoke stayed in! I turned the set off and attached a signal cable and re-applied power. It still worked. I turned it off and disconnected all the cables. Now I had to fix the stand.

The Stand

The stand is attached to the body of the set by brackets at the bottom left and right of the set. The screws are supposed to go through the case, through the bracket on the set and attach to the stand which is tapped. I hoped I could get some new screws, dress the threads in the stand and be on my way. No such luck. It turns out that the screws attaching the set to the stand were a “fine” thread pitch. Most screws in common use are “national coarse (NC)”, in fact all the other screws on the set were NC.

I went to the local hardware store which is excellent in their selection, and has knowledgeable sales people but they didn’t have any. They could special order them and I’d have them within a week or so. I checked with several other stores and finally found suitable replacements at a store that is about 13 miles and a 30+ minute drive from here. I could buy them for $0.31 a piece. I didn’t relish the idea of spending an hour in the car. Other options?

I wanted to see if I could drill and tap the stands to a larger size. Because two of the holes were partially stripped I was going to have to upsize at least 2 sizes… I ultimately decided on drilling and tapping two new holes in each leg using a larger size screw with NC threads.

After carefully measuring, drilling and tapping the holes, I was ready to start re-assembly of the set. To make assembly easier, I disassembled the stand, removing the legs from the base. I also marked each leg as I know my craftsmanship is not the greatest and although I tried, I doubt the two legs are identically fabricated. If I should need to take it apart again, it will go together a tad easier without me having to figure out left and right again. It took me about 45 minutes to drill and tap the four holes so I saved myself at least 15 minutes. (I’m sure I would have spent a bunch of extra time in the store looking at all the things they had for sale)

After attaching the legs, I finished by installing the rear cover. Lastly, I fixed the base to the legs. I got some help and lifted it back up into position in the family room.  The kids are happy again.

Documentation

I’ve been talking about this for a while.  I even offered up some suggestions in my previous post about how to possible modify the trouble shooting procedure.  Here’s another alternative.  I’ve used both methods and, for me, it’s a toss up.  I think I prefer this method a tad bit more as I can enter the data more easily into a spreadsheet. 

That means you would want to identify the procedure you used as well as the revision. 

REVISION? 

                                   What the heck are we revising? 

Let me explain.  To be certain of everything you’re doing and reconstruct things in the future should you ever need to, you must document what you did.  At the same time, if you don’t write a perfect procedure on your first try (I never have in over 25 years of writing and documenting procedures) you’ll need or want to change it. 

When supervising a large team it is imperative that everyone use the best known methods (BKM) when working.  This allows the collective intelligence of the group to be utilized everytime something is being worked on. 

You want  the organization to be a learning organization.  Someone once said of human beings that you are either learning or you’re dying.  The same could be said about an organization.  It is also said that  a business is either growing or dying. 

How does an organization learn anything?  Well, when any part of the organiation  learns something that has to be transferred to the rest of the organization.  How about saying that in English?  Well, what I mean is that if any individual within the organization learns something (improves a procedure, changes the order, adds a test fixture that speeds some step up or improves the accuracy of a step) the organization hasn’t learned it, yet.  The individual may have improved, but the organization has not.  The organization can be said to have learned it when that new knowledge is incorporated in the procedure that the organization uses AND everyone in the organization performing that procedure knows about and uses the changes to their, and the organizations, benefit.  If it is particularly complex or re-arranges a large number of steps or some other major difference, there may need to be training for other team-members that will be performing that same procedure. 

Perhaps you get a new piece of test equipment.  Maybe you get a new computer program.  How about a new power supply that is programmable when all you used to have is one that had a voltage adjustment?  Maybe a full on solder rework station that has integral vacuum and has a hot air pre-heat and hot air main heat?  If it is a big enough change, just writing it down won’t be good enough.  You’ll need to have training. 

Here’s an example of a learning organization.  I was assigned to a 688 class submarine that had just completed it’s commissioning shakedown. (it was brand-spanking new, everything was shiny and and…)  We took it into the shipyard to have a bunch of improvements made to it that weren’t included in the original, new construction, contract.  One of those items was to add  an anechoic coating to the hull.  This helped to make the ship quieter and stealthier.  When the shipyard did the procedure the first time, it took a long time.  The engineers that designed it gave there best guess as to how it should be installed and the time that it would take.

The actual shipfitters worked carefully, diligently and got it installed but it took LONGER than forecasted by the engineers.  The second ship was a little faster and by the time they got to the fourth ship they were at the time targetted by the engineers.  Everyone was elated.  The workers doing the actual work had another idea though.  They worked on improving the procedure.  They got permission from their superiors to try something.  After everyone agreed, they went to work.  Using their new procedure and an installation jig that a couple of them made in one of the machine shops they reduced the time by another 20%.  A couple more folks got involved and threw in their ideas.  By the time they competed three more ships they were doing the installation in 65% of the time allotted by the engineers.  All of these changes were incorporated into the new procedure.  The organization had learned. 

Shipyard management was so happy that they gave the installation team some really HUGE bonuses.  They were saving the company loads of  time.  (Everyone knows that time is money)  This allowed the shipyard to do the same job with fewer people and kept the upgrades on time and schedule.  The shipyard was also able to pass savings on to the Navy which means the american taxpayer was getting more for their money.  Everyone was happy.

This is why I recommend you have procedures that you actually use.  Periodically, review the procedure against the actual work being performed.  If it doesn’t match, figure out why. 

• Has the person doing the work made an unapproved change?
• Does the difference improve or detract from the standard output?
• Should the procedure be updated to reflect this new technique or change or should the person doing the work be re-trained on the correct procedure?
  1. If training is held, be sure to include the WHY, most people do much better(remember longer, perform more accurately, etc.) if they understand why something is being done in a particular manner. 
  2. If the procedure is to be updated, make the changes and train everyone else so that they can benefit.  Remember, the whole organzation benefits from the learning.

Here are a couple of filled out copies of the log that I use when trouble shooting just about anything.  As I mentioned above, I often do it directly in a spreadsheet for ease of cataloging.  Hope this helps.

trouble-shooting-log

trouble-shooting-log_tiller

So How did you do?  Did you build you troubleshooting guide for no Power?  Did you start?  I hope so, the best way to do anything is to “jump in” with both feet or “go for it”. Nike’s ad is in a similar vein: “Just Do It”

As promised, I’ll show you my troubleshooting guide:  troubleshooting-procedure_no_power  It is a Microsoft Word document so you can take it and adapt it for your own use. 

Some notes as you read through the procedure.  I tried to make it as generic as possible without becoming overly complex.  If you have a specific appliance down to the make and model, you can make a very concise procedure that is specific to your appliance.  You need to have some common sense while using this.

Notes:

1. Does the device have a power applied indicator?  A couple of my PC’s have lights on the back near the power connector that light if AC is applied.  Others show power on by lighting or blinking the LED’s on the front some have no indication.  Only our newest TV has a power applied LED visible when power is applied but the set is “OFF”.  It is actually indicating that the power supply +5Vsb (standby) is on
2. When checking fuses, always use an ohm meter.  I’ve seen fuses where the link was broken below the glass envelope and so visually appeared to be good.
3. Most consumer appliances, TV’s VCR’s etc included do NOT have fuses accessible from outside the cabinet.
4. The standard legal disclaimer is don’t attempt any of this unless you’re qualified to do so.  I can’t judge or validate your capability from behind a computer screen.  You’re a big boy or a big girl and need to make your own responsible decision. 
5. I recommend having a printed out copy right beside you as you do your work.  Re-arrange the cells so that you have room to write in them.  Make this a working document. 
6. I recommend adding a column for the date & time.  You might even have a start/stop time.  It will allow you to evaluate yourself or your staff’s ability to accurately & quickly perform the steps.   If you add enough columns you might want to change the orientation of the paper. 
7. Notice that the footer of the document tells you a couple of things.  It tells you the title of the document so you can find it on your computer when you forget where you saved it and, it tells you how many pages there are so you can ensure that you have the entire procedure every time you use it.  I use this so often for my procedures that I have created a macro that does the footer for me automatically.  You might want to do the same.

If for some reason you can’t open the document, let me know and I’ll convert it to pdf and post that version too.  Again, you should really have it as a document that you can manipulate, change and edit.  Till next time…  RD

As I think of tips I’ll post them and once I get enough, I’ll collect them on a single page so that they’ll be easier to find.  You may have noticed some random part numbers appearing on the site.  Since I’m always taking things apart and figuring out what they do, I’ve decided that I’d start posting any of the datasheets that I research on my website.  I don’t intend to be a “one stop shop” or complete repository, but as I figure things out, I’ll post the datasheets here.

First Tip:

As you take things apart, photograph them with a digital camera.  Do it with good lighting and, if appropriate, write yourself some notes:  “…when I pulled the back off the three screws across the top were longer than the four across the bottom.”  I’ve been doing this ever since I got my first digital camera.  It only had a 480 x 640 resolution and had no screen to see how the image turned out, but still I used it.  It has been indispensable.

1a. As you’re disassembling, if you don’t want to write yourself notes, use a voice recorder, your cell phone, MP3 player or any other device you have that allows you to record your voice.  My cell phone is a TREO 650 that I installed a voice recorder program on.  I set the file naming to include the date and time.  I don’t even have to think about what I’m doing.  Press a couple of buttons and I’m recording.

Moving parts

Tip 2 relates to moving parts.  I had a CD changer that would become difficult to open.  What I did was dis-assemble the case and then arranged it on the dining room table with LOTS of light and I set my VHS video camera up on a tripod over the mechanism.  The camera had a “high speed” mode which I engaged.  I then cycled the CD player until the mechanism stuck.  I was able to play the tape back and figured out what was causing the problem.  Mind you this was a 1989 vintage consumer camcorder, so high speed wasn’t like the ones they use on Myth Busters to catch the bullet tearing apart the crash test dummy.  So anything you can buy today will probably work.  Give it a go!

Saving screws…

For tip 3 you need to do a little assembly.  You’ll need:

• Shoebox lid (bigger is better)
• Some super-strong rare-earth magnets
• glue
• 3×3 Post-it notes
• pen, pencil or marker

Glue the magnets to the top(outside) of the lid several inches apart, at least 4.5″ apart.  Hopefully you have big feet and can get six or more magnets on the lid.  After the glue dries, turn the lid over and mark where the magnets are.   You’re ready to go.  The next time you take something apart, write on the post-it note where the screws came from: (top cover, bottom cover, HV shielding, power supply mounting, etc.)  stick it over one of the magnets and then put the screws on it.  The magnet should hold them in place, on the post-it note until it’s time to put it back together.  Other things you can do is number the post-its to correspond with the order, you could name the parts they go to, you could write down the inventory of screws for that step.  Remember, the more information, the better.  After reassembly, you can throw out the post-its.  OR, if you’re really clever, you’ll save all the information you wrote down into a notebook (database) so that you’ll have the information for the next time that make and model comes in the shop.

A simpler alternative is to use either a muffin baking tray or an empty egg carton. These have the advantage of being very easy, but it’s somewhat harder to categorize and classify information about where the screws came from.

(…continued)As I mentioned at the end of the last post, I’ve never owned an electronic repair shop.  In addition to all the things I mentioned in that post, I’ve worked in the military aboard nuclear submarines, I’ve worked in the chemical industry and the semiconductor industry.  In every case, the success of the organization has come down to the ability to doing the right thing, correctly, the first time, every time.

I can’t imagine any organization or business that wouldn’t have

• My garden tiller is hard to start.  Once it starts, it runs fine for about 10 minutes at which point it stalls if it is taken past half throttle.   If it is picked up so that the engine can run unloaded, it runs fine.  Again, once loaded it bogs down and quits. I’ve cleaned the air filter, fuel filter and spark plug.
• The TV works fine for some period of time and then just shuts itself off.  If turned back on, it makes a loud screeching sound for about a second and then runs.  It will shut itself off again, in less time than before. This continues with the time getting shorter and shorter till it gets to the point that it runs for about 6 minutes max.
• The dryer won’t turn.  I can hear the motor running and it blows air but the drum won’t turn…
• The computer boots but the shuts off after 15 minutes.  When first restarted it goes to “safe” mode.

Questions? Let’s ask questions!!

Don’t be shy about asking questions.  When you go to the doctors office because you don’t feel well, they don’t just give you a shot and send you home.  They ask you questions about your symptoms, they take some objective information about you like:

• Height
• Weight
• Blood Pressure
• Pulse
• Temperature

When you get to the doctor, who’s seen all the information, they usually start with an open ended question like “I see from the notes that this started several days ago, describe how you feel now…” All the while, they’re looking in your ears, nose, throat and perhaps listening to your heart and lungs.  They then probably ask more specific questions:

• Is it only on the right side?
• Always on the right or does it “move around”?
• Does the intensity change?

In some respects, the doctor’s job is easier.  They can ask questions to get information.  The questions can be in random order.  As an electronics repairer, you get one chance to ask questions (usually) and the answers tend to be less than definitive.  You can’t talk to the device, you have to probe, prod and investigate.  Back we go…

Beginning the repair

Based on the symptoms, you would want to ask additional questions, perhaps, or just dive right in.  The thing you want to develop is a troubleshooting matrix.  What I mean by this is something that reminds you of what to check first.  Just like the owners manuals for most appliances that tell you go over the simple things first (my washing machines manual):

• Is it plugged in?
• Is the circuit breaker turned on?
• Is the water turned on?
• Is the lid/door shut?
• Is the load unbalanced?
• Is the child lock activated?

If you are going to run an electronics shop the most common complaint will be:

It won’t turn on

You want to check the obvious and simple things quickly as you don’t want to march off down the wrong path and start removing components when the thing just needed a new fuse.  The perfect examples I have of this are:

• A friends’ toaster oven quit working. It turned out to be the thermal fuse.  Trouble shooting time was  under 10 minutes.
• Another friends’ toaster quit working.  The problem ended up being that the line cord had broken internally. Trouble shooting time 2.5 hours.

In one case, you can tell your customer that you want $25 for the repair.  In the other case, if you tell them $200 to repair, they’ll laugh and go buy a new one.  In the second case, if the trouble shooting had started with: is there power inside the toaster?; the time would have been substantially less.

Homework

So the thing you want to have is a logic diagram that has you check the common things quickly & thoroughly.  Here is your homework assignment:  Make yourself a troubleshooting logic diagram that covers the first part of a repair, isolating a power problem.

At the below left is a sample logic diagram. It represents entering a room where you want to turn on a lamp that is connected to the wall switch next to the entrance doorway.  It is not all inclusive, (it never asks if the power is on to the room circuit), but it give you an idea of the overall thought process for getting the light illuminated in the room.  Click on the image to view it full size.

I hope this helps you with your diagram. Don’t worry about getting it perfect at this point, don’t worry if you only have a couple of things to check.  The important thing is to start thinking about it and documenting (writing it down) your thought process.  The next thing we’ll create is a troubleshooting checklist, based on this diagram.

Additionally, we’ll create a troubleshooting log.  This will be a uniform way of writing down what it is that you have done and what the results are.  For involved, complex,  troubleshooting this is one of the most important things to have.  Why?  If the problem is complex enough that you can’t solve it in one session, you’ll want to be able to easily remember where you were and what you did or didn’t do.  Or, more likely, if you are just starting out you have to do everything.  You have to answer the phone, you have to answer the door and deal with whatever distractions come your way.  If the distraction is important, you may decide to keep dealing with it, or with something related to it, rather than resuming your troubleshooting immediately.  Having a consistent way of doing the troubleshooting and documenting it will be helpful.  Looking to the future, when you aren’t the one answering the phones, you will likely have an apprentice or two.  If they get stuck or can’t figure something out, it will be immensely easier for you to troubleshoot if you have a well documented log.  Or perhaps you want the two or three apprentices to trade off on their troubleshooting, again this will be a useful tool. 

OK, write up your diagram.